1. Field of the Invention
The present invention relates to an image forming apparatus for recording an image on a recording medium.
2. Description of the Related Art
Conventionally, an image forming apparatus is well known for forming a color image on a recording medium by jetting liquid ink of each color, for example, black (K), cyan (C), magenta (M), and yellow (Y) onto the recording medium from an ink head group including a plurality of ink heads mounted in an image forming apparatus.
In the image forming apparatus, a belt platen is provided as a feeding mechanism for feeding the recording medium. Provided above the belt platen is a recording unit for holding ink heads for jetting the liquid ink of the respective colors of black (K), cyan (C), magenta (M), and yellow (Y). The ink heads are fixed at predetermined intervals in the feeding direction of the recording medium for each color.
The belt platen has, for example, an endless belt, and the belt is put on between a driving roller and a driven roller. A tension roller maintains tension from inside the belt. The belt platen is configured to cyclically move the belt in a predetermined transfer direction by the driving rotation of the driving roller and the driven rotation of the driven roller and the tension roller.
The belt platen is feeds a recording medium below the ink head group with the transfer of the belt while adsorbing and holding the recording medium onto the belt when the recording medium is carried in. The ink head group jets the ink onto the recording medium fed downward, and forms an image. The recording medium on which the image is formed is fed by the belt platen, and ejected outside the apparatus.
As an image forming apparatus described above, for example, a common base unit is provided for the body of the apparatus in addition to the belt platen and the recording unit, and a positioning operation is performed by arranging the belt platen and the recording unit such that they come in contact with the base unit (for example, Japanese Published Patent Application No. 2004-161477).
Another conventional technique is, for example, an image forming apparatus for forming a toner image using a recording unit designed in an electronic photographic system on a recording medium in paper sheet form and fed by a belt platen.
In the above-mentioned image forming apparatus, a feed roller (hereinafter referred to as a “resist roller pair”) is provided for regulating and amending the tilt (deviation in a feed path etc.) of the feeding direction of a recording medium at the feeding position of the recording medium of the belt platen (at the upstream in the feeding direction of the recording medium).
The resist roller pair suppresses the feed of the recording medium supplied from a paper feed device by temporarily stopping it for synchronization with the image forming timing of the recording unit, and introduces the recording medium to the belt platen by resuming the rotation in synchronization with the image forming timing.
After the feeding posture of the recording medium is corrected using the resist roller pair, the recording medium is fed to the belt platen, and adsorbed onto the belt by the adsorbent property of the belt platen.
Furthermore, the toner image is transferred to the recording medium fed by the belt platen. The recording medium to which the toner image is transferred is carried from the belt platen to a fixing device. In the fixing device, the toner image is fixed on the recording medium, and the recording medium is carried by a feed roller pair and ejected outside the apparatus (for example, refer to the Japanese Patent Publication No. 2731963).
The Japanese Patent Publication No. 2731963 discloses the recording unit having only one photosensitive material. However, as in the case of the Japanese Published Patent Application No. 2004-161477, there is an electronic photographic image forming apparatus of tandem type in which four photosensitive materials of black (K), cyan (C), magenta (M), and yellow (Y) are arranged in multi-stage form at predetermined intervals in the feeding direction. They have almost the same configuration except the number of photosensitive materials, that is, one photosensitive material or four photosensitive materials.